| Project/Area Number |
16370019
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
植物生理・分子
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| Research Institution | Nara Institute of Science and Technology (2006)
The University of Tokyo (2004-2005) |
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Principal Investigator |
UMEDA Masaaki Nara Institute of Science and Technology, Graduate School of Biological Sciences, Professor, バイオサイエンス研究科, 教授 (80221810)
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| Project Period (FY) |
2004 – 2006
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| Project Status |
Completed (Fiscal Year 2006)
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| Budget Amount *help |
¥15,400,000 (Direct Cost: ¥15,400,000)
Fiscal Year 2006: ¥4,600,000 (Direct Cost: ¥4,600,000)
Fiscal Year 2005: ¥4,700,000 (Direct Cost: ¥4,700,000)
Fiscal Year 2004: ¥6,100,000 (Direct Cost: ¥6,100,000)
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| Keywords | Plant / Cell proliferation / Cell division / Cell cycle / Cyclin / Phytohormone / Morphogenesis / Signal transduction / サイクリン依存性キナーゼ / CDK活性化キナーゼ / サイクリンA / Weelキナーゼ |
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| Research Abstract |
In this project, we aimed to reveal the cell cycle control in response to cytokinin signaling in plants. First, we conducted a functional analysis of CDK-activating kinases (CAKs) that phosphorylate and activate CDKs. Our results showed that CDKD is an orthologue of vertebrate-type CAKs, while CDKF is a plant-specific type of CAK which possesses the CAK activity but not the CTD-kinase activity. CDKF can also phosphorylate CDKD and constitutes a CDK-phosphorylation cascade that exists only in the plant kingdom. Arabidopsis cdkf mutants showed severe defects in cell division, cell elongation and endoreduplication. Identification of CDK activators by using a S. pombe mutant revealed that ARR4 may be involved in CDK activation. ARR4 is a member of the A-type response regulators that are associated with cytokinin signaling, thus further studies will clarify the interaction between cytokinin signaling and CDK activation by CAKs.
Plant cyclin A3 (CYCA3) exhibits a peak of gene expression during the G1-to-S phase. We found that the expression of two of the four Arabidopsis CYCA3s, namely CYCA3;1 and CYCA3;2, were up-regulated in response to cytokinin. Each CYCA3 has an ability to bind and activate CDKA, and the associated kinase phosphorylates the Rb protein. On the other hand, we noticed that overexpression of CYCD4 in Arabidopsis hypocotyl segments resulted in promotion of callus formation in the tissue culture system. These results indicate that CYCA3 and CYCD4 may receive the cyctokinin signals and transmit them to the cell cycle machinery to activate cell proliferation.
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